1. The Field of the Invention
The present invention relates to a method and apparatus for recovery of hydrocarbons from a reservoir by steam flooding and in particular to a method and apparatus which will reduce steam override thereby providing a cleaner steam sweep of the reservoir.
2. The Prior Art
Steam flooding has become an accepted practice for the recovery of heavy petroleum from fields or reservoirs that require a thermal stimulation to produce a satisfactory flow of crude. There is a need for a simple method to assure that the reservoir will be completely flooded with the steam. In the usual scenario the steam entering the formation from an injection well will tend to rise towards the surface as it moves out through the formation from the injection well. The further out the steam travels from the injection well, the further up towards the surface it will flow. When the steam encounters an extraction well, it will be at a shallower depth than the point at which it was injected. This is called steam override and leaves a portion of the formation still containing hydrocarbons which cannot be recovered by further steam injection since any additional steam would merely follow the previously swept path.